Automatic control apparatus for aircraft



June 16, 1-942. F. w. MEREDITH AUTOMATIC CONTROL APPARATUS FOR AIRCRAFT Filed July 7, 1939 3 Sheets-Sheet l June 16, 1942.

Filed July 7, 1939 F. w. MEREDITH AUTOMATIC CONTROL APPARATUS FOR AIRCRAFT 3 Sheets-Sheet 2 June16, 1942. F. w. MEREDITH 2,286,561

AUTOMATIC CONTROL APPARATUS FOR AIRCRAFT Filed July '7, 1939 3 Sheets-Sheet 5 q E O 0 j sary to precess the gyroscope when the aircraft 2:

to the vertical, e. g. horizontal for controlling Patented June 16, 1942 AUTOMATIC ooN'rRoL APPARATUS moam Frederick William Meredith, London, England, assignor to S. Smith & Sons (Motor Accessories) Limited, London, England, a British company Application July 7, 1939, Serial No. 283,313

In Great Britain July 13, 1938 i 8' Claims. (Cl. 244-79) This invention relates to automatic control apthe aircraft about a horizontal axis, precessing paratus, for aircraft, of the kind in which a gymeans for applying a torque to the gyroscopic roscope with its rotor axis inclined to the vertical device about said horizontal axis, means auto- (e. g. horizontal) is arranged to control the bank matically controlling the aircraft about a secor pitch of the craft. 5

If a rotating body (for example, the rotor of a gyroscope) is subjected to a torque about any axis, this torque may be resolved into two components; one component about the axis of rotation and the other about an axis normal to the axis of rotation. The first component merely alters the speed of rotation of the body and the second component causes precession of the axis of rotation about an instantaneous axis (hereinafter termed the axis of precession") normal both to the axis about which the said second component operates and to the axis of rotation. The said second component of torque is therefore referred to hereinafter as the "precessing torque. Thus, the axis of rotation, theaxis of precession and the axis about which the precessing torque operates, together form an orthogonal system.

In apparatusof the kind described, it is neces- FOR through a distance corresponding to the angle of movement of the aircraft about said second horizontal axis and a coupling connecting said 10 precessing means through thesaid angle so as to maintain the torque axis substantially horizontal. If the said part rotates through the said angle the yroscopic device may conveniently be mounted on this part so as to rotate therewith. In one form of the invention the means for controlling the aircraft about the second horizontal axis comprises a second gyroscopic device having its rotor axis inclined to the vertical and 20 on a common platform which is supported in the aircraft for movement about the two said horizontal axes or axes parallel thereto. Thus. rotation of the platform about eitherof these axes causes the appropriate gyroscope to rotate the craft about that axis through a corresponding angle and at the same time rotates the other gyroscope, and with it its precessing means relative to t e craft through the same angle so as to mainta n the precessing torque axis horizontal. The primary feature of the invention, as aforesaid, is thus applied to both gyroscopes- According to a further feature of the invention, whereby substantially correctly banked turns at the assigned angle of bank may be attained, one of said gyroscopic devices also controls the rudder of the aircraft and means, operchanges course so as to maintain the azimuthal configuration of the rotor axis with respect to the craft when the heading of the craft is altered. It is desirable that the axis of precession and the rotor axis should lie in the same vertical nane,- as otherwise the inclination of the rotoraxis to the vertical will vary and the bank or pitch datum will be changed. This necessitates the application of the precessing torque about a horizontal axis, and for this purpose it is known to provide means for applying a precessing torque about an axis fixed in the craft. The torque axis, however, may not remain horizontal if the craft is not flying level and the object of the present invention is to overcome this difficulty and so enable the craft to be turned while banked or pitched.

In addition to the said gyroscopic control apparatus, it is usual to provide additional appaiatus (which may or may not also be gyroscopii: cally controlled) for automatically controlling the craft about a second horizontal axis. That is to say, if the gyroscopic control apparatus controls the craft in pitch the additional apparatus controls it in roll and vice versa. I 0

According to the primary feature of the present invention there is provided a control apparatus for aircraft comprising a gyroscopic device in which the rotor axis is normally inclined Zil is provided sensitive to lateral acceleration or side-slip for controlling the precessing torque apm plied to this gyroscope so as to adjust the rudder to reduce the lateral acceleration or side-slip. By lateral acceleration is meant the component of the total acceleration field (as measured for the lateral axis of the craft.

Yet another feature consists in providing means controlled by rotation of the said platform about one of said axes or an axis parallel thereto for bank control of the craft, for diverting the control provided by said means, sensitive to said lateral acceleration or side-slip to means for prebank trimming of the aircraft when the said platform is not displaced.

55 One form of control apparatus according to 0nd horizontal axis and having a part rotatable,

part to the said processing means to rotate the the two gyroscopic devices are mounted together example by accelerometers) in the direction of cessing the gyroscope for bank control to effect ative when the aircraft is intentionally banked,

the invention isshown diagrammatically and by way of example in the accompanying drawings, in which:

Figure 1 is a general view of the apparatus; Figures 2 and 3 are detail vlewsi and Figure 4 shows a modified control apparatus. Referring to the drawings, a platform I is pivotally mounted by spigots in -a frame l2 for rotation about a normally horizontal axis Y.

The frame I2 is rotatably mounted by means of spigots |3 located in bearings l4 fixed in the aircraft such that the axis X, about which the frame H can turn, is horizontal and lengthwise of the craft. The platform I0 is guided for movement about the axis Y by a column I5 engaging in a slot IS in an arcuateguide pivoted about an axis which coincides with the Y axis when the frame I2 is in the horizontal position.

The platform I8 carries a gyroscope I00 for controlling the craft in pitch, this gyroscope comprising a rotor l8 whose axis of spin is horizontal and lies fore-and-aft of the craft. The rotor I8 is carried in bearings in a gimbal ring l9 arranged horizontally and. in turn pivotally mounted in an outer gimbal ring 20 which is rotatable about a vertical axis on the platform I0.

The inner gimbal ring I9 is connected by a link 2| to a valve 22 which controls a supply of air under pressure to a servomotor. not shown, for

- adjusting the elevator of the aircraft in known manner, the link permitting the necessary movementabout the pivotal mounting of the outer gimbal ring 20. The outer gimbal ring 20 is unbalanced by a weight 23 and it is connected by a link 24 to a valve 25 controlling a supply of air under pressure to a servo-motor, not shown, for operating the rudder in known manner.

Also mounted on the platform I8 is a gyro scope 200 for controlling the ailerons of the aircraft. This gyroscope comprises a rotor whose axis of spin is horizontal and lies transversely of the aircraft. The rotor is carried in hearings in an inner gimbal ring 3|, the plane of which also lies transversely of the aircraft and this inner gimbal ring is pivotally mounted in an outer gimbal ring 32 which is pivoted for movement about a fore-and-aft horizontal axis on the platform It. The outer gimbal ring 32 is connected by a link 33 to a valve 34- controlling the supply of air under pressure to a servomotor, not shown, for operating the ailerons of the aircraft. The inner gimbal ring 3| is connected by a.link 35 to a detecting valve 36 for controlling the air supply to a precessing motor 37 mounted on the platform I. This motor operates on the outer gimbal ring 32 through a link 38.

On the frame |2 there is a bracket 40 carrying a delivery nozzle 4| for air under pressure and opposite to it a receiving nozzle 42. A blade 43 movable between these nozzles controls the air pressure in the conduit leading from the nozzle 42. The blade 43 is mounted on a weight 44 which is carried by means of springs 45 connected to a member 48 is mounted on a spindle 41 rotatable in the frame |2 about the X axis. The member-4G also carries an electric contact brush 48 co-operating with a commutator 49 on the frame l2, this frame having interconnected contacts 50 and 5| separated by an insulating section 52. The brush 48 normally rests on this insulating section.

nected to the contacts 50 and 5|. 55 controlled by themagnet 54 is connected to the spindle 55 of a change-over valve 51.

The valve has an inlet 58 which is connected. to the nozzle 42 and another inlet 59 to which air under pressure is applied through a reducing valve 60. According to the position of the blade 43 between the nozzles 4| and 42, the air pressure'applled from the nozzle 42 to the valve varies within a range extending above and below the pressure applied at the inlet 59. The valve has outlets 62 leading to a bank trimming motor 10 carried on 'the platform I0 and having an operating link connected to the inner gimbal ring 3| of the gyroscope 200. The valve has other outlets 12 leading to an azimuth precessing motor I3 having an operating link 14 connected to the inner gimbal ring IQ of the rudder and elevator gyroscope I00, the link permitting the necessary movement about the pivotal mounting of the outer gimbal ring 2|]. In the energised position of the magnet 54 the movable element 53 of the valve is in such position as to connect the inlets 58 and 59 to the precessing motor 13 and in the de-energised position the trimming motor 10. The blade 43 has one edge normally lying across the centre of the nozzle 4|, so that the difference in pressure at the inlets 58 and 59 of the valve has a zero value at the normal position and an increasing value upon relative movement of the blade and the nozzles and depending in sign upon the direction of this relative movement.

By means of the apparatus according to this invention the control of the aircraft in pitch and roll is effected by means such as the pulley .and cable for turning the platform about the X axis, and another pulley and cable 8| for turning the platform about the Y axis. By rotation of the platform l0 about the Y axis it is displaced from its horizontal position in the aircraft so as to produce by means of the gyroscope Hill a corresponding change in the elevational direction of the aircraft. Similarly, by rotation of the platform l0 about the x axis, displacing it from the horizontal position in the aircraft, there is produced a control of theaircraft in bank.

By turning the frame about the X axis, the relative displacement of the platform l0 and the outer gimbal ring 32 of the gyroscopic device 200 operates the valve-34 for producing an adjustment of the ailerons to bring the platform It] back to the normal horizontal position by banking the aircraft. This banking of the aircraft produces side-slip which is detected by the weight 64 displacing the blade 43- with respect to the nozzles 4| and 42. The air pressure in the conduit 58 leading from the nozzle 42 will thus be increased or decreased as the case may be. Since the frame |2 has been turned in the aircraft the circuit of the magnet 54 is energised through the brush 48 and one of the contacts 50, 5|, so that the valve 51 applies the air pressures at the inlets 58 and.59 to the azimuth precessing motor 13. The motor transmits a torque to the inner gimbal ring I9, causing the rotor to precess. The resulting precessional movement of the outer gimbal ring 20 operates the valve 25 to energise the servomotor for moving the rudder to turn the aircraft in such a sense as to limit the side-slip causing the said displacement of the blade 43.

Thus, the weight 44, its associate jets 4| and 42 and the azimuth precessing motor 13 together form a governor to control the extent of side An armature above the axis of rotation of the frame I2, so

that when the frame I2 is inclined about its axis X, to initiate a turn, the jets are displaced relative to the blade 43 even though the side-slip is zero. v

In straight flight the'contact 48 is open and outer gimbal ring I04 rotatable about a vertical axis. The inner gimbal ring I03 is connected by a link I05- to a valve I06 controlling a supply of air under pressure to a servomotor I01 containing a double-acting piston, of which the piston rod I08 is connected to the elevators. 'A followup is provided through a fluid coupling I09 connected to one arm of a lever IIO, the other arm of which is connected through a link III to the cylinder of the valve I06. Centering springs I I5 and H6 are provided for the follow-up mechathe pressure difference in the conduits 53 and 59 is applied to the bank trimming motor I0 for the purpose of ensuring correct levelling of the platform l0 about the axis X. Thus, if the plat form I is slightly tilted about the X axis, the

blade 43 is displaced relative to its associated jets and the pressurein the conduit 58 isno longer equal to pressure in the conduit 59 and so" that the motor I0 applies a torque to the inner gimbal ring 3|, so as to precess the outer gimbal ring 32 to change the attitude of the craft until the platform I0 is correctly levelled about the X axis.

By adjustment of the pitch control 8I the platform I0 is displaced relative to the gyroscope I00 about the axis of the inner gimbal ring and the consequential relative movement of this inner gimbal ring and the platform I0 controls the, valve to .produce amovement of the elevators to tilt the craft so that the platform is-returned to the horizontal position. If, however, the platform I0 is slightly tilted about the Y axis the weight 23 applies a torque to the outer gimbal ring which precesses the inner gimbal ring I9 thus changing the attitude of the craft until the platform is correctly levelled about the Y axis.

It will thus be appreciated that the platform I0 on which the gyroscopic devices are mounted is. always returned to the horizontal position regardless of the trim of the aircraft so that in the case of each gyroscope the axis of precession during a turn is maintained vertical and thus lies in the same vertical plane as the rotor axis.

The -bracket 46 which carries the electric contact brush 48 is mounted on a spindle 41 which is normally fixed with respect to the frame I2.

It may, however, be rotated through a pulley 82 and cable for producing a fiat turn of the aircraft, in which ,case thevpulley 80 is held fixed.

In other respects the gyroscopes I00 and 200 perform their well known functions, operating in the known manner for the control of the rudder and elevators, and the control of the ailerons respectively, for instance, as described in Great Britain Patent No. 365,186 and United States Patent No. 1,992,086.

It will be understood that known means may be employed to provide a follow-up from each servomotor to its associated valve, although for clarity such follow-up means are omitted in Figures 1 to 3.

In Figures 1 to 3, the rudder gyroscope controls the elevators, but the modifications necessary when the rudder gyroscope controls the ling the craft in pitch has its rotor I02 arranged with the axis of spin horizontal and fore-andaft of the craft. The rotor is mounted in bearpiston rod I28 is connected to the ailerons. A

nism. An azimuth precessing motor I I2 mounted on a plate II3, which is rotatably mounted for movement in a vertical plane, operates on the gimbal ring I03 through a link II4. Air under pressure is applied to this motor under the control of means (not shown) for detecting precession of the outer gimbal ring I04 due to movements of the craft in pitch, so as to maintain the azimuthal configuration of the rotoraxis with respect to the craft. v Another gyroscope I20 for controlling the ailerons of the aircraft comprises a rotor I2I whose axis of spin is horizontal and lies transversely of the aircraft. Thisrotor is carried in bearings in an inner gimbal ring I22, which is rotatable about a vertical axis in an outergimbal ring I23. The outer gimbal ring I23 is pivotally mounted about the roll axis in a follow-up frame I24 also pivoted about the roll axis. The follow-up frame carries a piston valve I25, of which the piston is connected by a link I26 to the outer gimbal ring I23. Thevalve I controls a supply of air under pressure-to a servomotor I21 containing adouble-acting piston, of which the follow-upis provided through a viscous coupling I29 connected to the piston rod and one arm of i a lever I30, the other arm of which isconnected to the follow-up frame I24. Centering springs I3I and I32 are provided for the follow-up frame.

. By means of this gyroscope, movement of the ings in an irmer gimbal ring I03 arranged horiframe I24, thus operating the valve I25 to move the'ailerons to oppose the roll.

For the purpose of this invention the follow-up frame I24 is coupled to the precessing motor II2 so that the latter rotates through the same angle as the follow-up frame. Thus, the follow-up frame I 24 has an extension I34 connected by a link I33 to the plate II3 carrying the precessing motor II2, so that rotation of the follow-up frame of the gyroscope I20 through any angle produces a rotation of the precessing motor II2 through the same angle. Thus, should the aircraft be flying in a banked attitude, the consequential displacement of th follow-up frame I24 produces a corresponding displacement of the precessing motor II2 which in turn rotates the inner gimbal ring of the gyroscope IN to maintain the axis about which the precessing torque operates, substantially horizontal.

Iclaim:

1. A control apparatus for aircraft, comprising a. gyroscopic' device having the rotor axis normally inclined to-the vertical, means operated by said gyroscopic device for controlling the aircraft about a horizontal axis, -precessing means for applying a torque to said gyroscopic device about said horizontal axis, said precessing means being rotatable about a second horizontal axis inclined to the first said horizontal axis, means automatically controlling the aircraft about said second horizontal axis and having a part rotatable through a distance corresponding to the angle of movement of the aircraft about said second horizontal axis and a coupling connecting said part to the said precessing means to rotate the precessing means through the said angle so as to maintain the axis about which said torque is applied substantially horizontal,

2. A control apparatus for aircraft'comprising a gyroscope control device having the'rotor axis inclined 'to the vertical, means operated by said gyroscope control device forfcontrolling the attitude of the aircraft about one horizontal axis, precessing means for applying a torque to said gyroscope about said horizontal axis when the craft is being turned, a second control device for controlling the attitude of the aircraft about a second horizontal axis, displacinglmeans for the datum of the second control device and means coupling said displacing means to said precessing means for the purpose of maintaining the attitude, of said precessing means about said second axis when said datum is altered.

3. A control apparatus for aircraft as claimed in claim 1, wherein the said part and said precessing means are mounted on a common rotatable member. I

4. A control apparatus for aircraft as claimed in claim 2, wherein the coupling comprises a rotatable member carrying both control devices.

5. A control apparatus for aircraft comprisaxes parallel with said horizontal axes, and is moved relatively to the aircraft about a said horizontal axis as a result of change of datum of a said gyroscope to maintain a given attitude of the precessing means of the other gyroscope.

'7. A control apparatus for aircraft comprising a gyroscopic device having the rotor axis normally inclined to the vertical, means oper-.

ated by said gyroscopic device for controlling the aircraft about a horizontal axis, precessing means for applying a torque to said gyroscopic device about said horizontal axis, a second gyroscopic device having the rotor axis normally inclined to the vertical, means operated by said second gyroscopic device for controlling the aircraft about a second horizontal axis, precessing means for applying a torque to said second gyroscopic device about said second horizontal axis. and a common supporting member on which both said gyroscopic devices and both said precessing means are mounted, which supporting member, is mounted for movement in the aircraft about axes parallel with said horizontal axes, and is moved relatively to the aircraft about a said horizontal axis as a result of change of datum of a said gyroscope to maintain a given attitude of the precessing means of the other ing a gyroscope control device having the rotor axis inclined to the vertical, means operated by said gyroscope control device for controlling the attitude of the aircraft about one horizontal axis, precessing means for applying atorque to said gyroscope about said horizontal axis when the craft is being turned, a second gyroscope control device, means operated by said second gyroscope control device for controlling the attitude of the craft about a second horizontal axis, and a common supporting member on which both gyroscope control devices are mounted, which supporting member is mounted for movement in the aircraft about axes parallel to said horizontal axes and which supporting member serves to transmit a displacement of the datum of said second control device to the said precessing means of the first said control device to maintain the attitude of the said precessing means about the second horizontal axis when said datum is altered.

6. A control apparatus for aircraft comprising a gyroscopic device having the rotor axis normally inclined to the vertical, means operated by said gyroscopic device for controlling the gyroscope, means controlled by one of said gyroscopic devices for operating the rudder of the aircraft, and means responsive to lateral acceleration or side-slip to control the precessing torque applied to this gyroscopic device so as to adjust the rudder to reduce the lateral acceleration or side-slip.

8. A control apparatus for aircraft comprising a gyroscopic device having the rotor axis normally inclined to the vertical, means operated by said gyroscopic device for controlling the aircraft in bank about a horizontal axis, precessing means for applying a torque to said gyroscopic device about said horizontal axis. a second gyroscopic device having the rotor axis normally inclined to the vertical, means operated by said second gyroscopic device for controlling the aircraft in pitch about a second horizontal axis, precessing means for applying a torque to said second gyroscopic device about said second horizontal axis, and a supporting memplied, to this gyrosc pic device so as to adjust the rudder to reduce the lateral acceleration or side-slip, means controlled by the rotation of said supporting member about an axis parallel to first said horizontal axis, to divert the control provided by said means sensitive to lateral acceleration or side-slip from the precessing means for controlling the rudder to said precessing means for first said gyroscope, for bank trimming of the aircraft.

FREDERICK WILLIAM MEREDITH. 

